Storage area networks (SANs) are typically implemented to interconnect data storage devices and data servers or hosts, using network switches to provide interconnectivity across the SAN. SANs may be complex systems with many interconnected computers, switches, and storage devices. The switches are typically configured into a switch fabric, and the hosts and storage devices are connected to the switch fabric through ports of the network switches that comprise the switch fabric. Most commonly, Fibre Channel (FC) protocols are used for data communication across the switch fabric, as well as for the setup and teardown of connections to and across the fabric, although these protocols may be implemented on top of Ethernet or Internet Protocol (IP) networks.
Many SANs rely on the FC protocol. The FC protocol defines standard media and signaling conventions for transporting data in a serial fashion. It also provides an error correcting channel code and a frame structure for transporting the data. Many FC switches provide at least some degree of automatic configurability. For example, they may automatically sense when a new inter-switch link (ISL) becomes active, and may initiate an initialization process to discover what the link connects to. The switch may automatically determine various parameters for the link (e.g. link speed). As FC networks are created, updated, maintained and de-commissioned, switches may be enabled, disabled or reconfigured, and links may be added or removed.
Over time, FC networks have become more complex, with multiple fabrics involving several switches that use inter-switch links (ISLs) connected to switch ports (E_ports) on the switches. As FC networks have become more complex, the network speeds have also increased significantly. As faster networks are implemented, media and cable tolerance become more important for avoiding degraded performance and cyclic redundancy check (CRC) errors. At the same time, as larger networks are developed, diagnostic of optics and cables become more and more time consuming and intrusive. Current switches have two basic types of built-in diagnostics. First, the SFP electro-optical modules have digital diagnostics, but these only operate at the SFP component level. Second, a command line interface (CLI) tool may be provided to allow frames to be injected and circulated on a specific link, but the end result is only a good and bad indication, which does not greatly aid diagnosis. An alternative way of performing diagnostics is to use a network link level diagnostic tool which involves utilizing a dedicated diagnostic port (D_Port). D_Ports are ports that are statically configured by the user for the purpose of running diagnostics. Generally, any FC port can be configured as a D_Port. However, once a port is configured as a D_Port, it will no longer be part of the fabric as it will not carry any inter-switch or data traffic. A D_Port will also not merge fabrics. The D_Port is only used for link diagnostic purposes and to isolate link level faults. The D_Port is only used for link diagnostic purposes and to isolate link level faults.
Some D_Ports have been recently developed that can dynamically enter into diagnostic mode. One such configuration is discussed in U.S. Patent Publication No. 2013/0266307, filed on Mar. 7, 2013 and entitled “Diagnostic Port For Inter-switch And Node Link Testing In Electrical, Optical And Remote Loopback Modes,” which is hereby incorporated by reference in its entirety. Though advantageous in certain aspects, such configurations still require that the link be disabled or de-commissioned for the duration of the diagnostics, and as such significantly interferes with regular traffic. Taking a link offline could also result in rerouting of traffic and can cause imbalances in the system.
An alternative way of performing online path diagnostics has been recently developed which involves testing of links between two HBAs or CNAs ports, by saturating one DMA channel between the two ports with diagnostic traffic while regular traffic flows through the other DMA channel. One such configuration is discussed in U.S. Patent Publication No. 2013/0111077, filed on Oct. 31, 2011 and entitled “SAN Fabric Online Path Diagnostics,” which is hereby incorporated by reference in its entirety. Though providing the ability to continue running traffic during diagnostics, this method is limited to use between HBAs. Moreover, because the DMA channel used for diagnostics is saturated with diagnostics traffic, regular traffic flows at a reduced rate.
Thus it would be desirable to implement a network diagnostic method to more efficiently troubleshoot larger networks, thereby improving the speed, efficiency, and reliability of these networks.